One
Newton (N) of force is defined as the amount of force needed to accelerate 1 kilogram
(kg) of mass at a rate of 1 meter per second squared (m/s2).

1
Newton = 1 kg m/sec2 (A kilogram is the amount of weight at which 1 N of force
will accelerate at a rate of 1 m/s2.)

--->>English
System: Pound (LB) 1 LB = 4.448 N

In English system of measurements, a slug is the amount of mass that 1 pound of
force will accelerate at 1 ft/s2, and a pound mass is the amount of mass that
1 LB of force will accelerate at 32 feet/s2.

Describing
a Force:

A
force is a vector
quantity. A vector quantity is a quantity which has both magnitude and direction.
To fully describe the force acting upon an object, you must describe both its
magnitude and direction. Thus, 10 Newtons of force is not a complete description
of the force acting on an object. 10 Newtons, downwards is a complete description
of the force acting upon an object.

(Note:
What is the difference between vector
and scalar quantities? A vector has both strength and direction, a scalar
quantity can be described using only 1 quantity, magnitude. Examples of scalar
quantities are: time, energy and volume since they only represent magnitude and
no direction.

What
is the Difference between Mass and Weight?

Shown
below are two types of scales commonly used in the classroom --a spring scale
(left) and a simple balance beam scale on the right.

On
earth the spring scale reads 100g with an unknown mass attached at the bottom.
To balance the scale on the right a 100g mass was also needed.

If
we were to take both scales to the moon, what would the the spring scale read?
How much mass would be needed to balance the 100g mass on the balance beam? Can
you explain your answer? For more details see the Mass
and Weight Page.

spring scale

simple
balance scale

What
does applying a Force do?

Force
causes acceleration.

Newton's
Second Law states that: the
acceleration (a) of an object is directly proportional to the force (F) applied,
and inversely proportional to the object's mass (m).

That means that the more force you apply to an object, the greater the acceleration.
And, the more mass the object has, the lower the acceleration.

Newton's
Second Law can be written in equation form: F = ma.

For
falling objects we can write F=mg where g is the acceleration due to gravity.
The force of gravity
is what causes free falling objects to accelerate. These objects all accelerate
at the same rate of 9.8 meters/sec^2

What
is Friction?

Friction
is the force that opposes the relative motion or tendency to such motion of two
bodies in contact. If we try to push a block of wood across a table, there are
two opposing forces
that act: the force associated with the push, and a force that is associated with
the friction which acts in the opposite direction. As
frictional forces are decreased (for example, by placing oil on the table) the
object moves further and further before stopping. This demonstrates Galileo's
law of inertia which states: an
object in a state of motion possesses an ``inertia'' that causes it to remain
in that state of motion unless an external force acts on it.

Try
these exercise!

1)
How much net force is required to accelerate a 1500 kg car at 6.00
m/s2?

Please
enter your answer in the space provided:

newtons

2) What
is the mass of an object that has a weight of 115 N on the Moon? The gravity of
the Moon is 1/6 of g (which is 9.8 m/s2).

kg.

3) An object in free fall will accelerate at a rate of :

m/sec/sec

Multiple
Choice Questions

1.
Which of the following are contact forces?
a) magnetic forces
b) gravity
c) air resistance
d) electrostatic forces

2.
Which of the following are action at a distance forces?
a) air resistance
b) normal forces
c) magnetic forces
d) frictional forces

3.
What is the
force that opposes the relative motion or tendency to such motion of two bodies
in contact
a) magnetism
b) the
normal force
c) gravity
d) friction

5. Which of the following statements is not correct
a) air resistance is a force
b) mass is the result of the force of gravity
c) to accelerate an object requires a force
d) weight is the force
of gravity